Investments in Real Estate Entities (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	$ 64,962	$ 70,018	$ 148,766
Gain on sale of communities	196,749	98,899	333,221
Fund I
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	87	871	475
Fund II
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	49,882	32,211	24,808
Equity in income of unconsolidated entities relating to the Company's recognition of promoted interest	7,985
Gain on sale of communities	41,501	29,726	21,624
US Fund
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	15,635	2,052	342
Gain on sale of communities	16,568
ACJV
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	1,445	511	1,579
MVPI LLC
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	1,627	22,453	1,651
Equity in income of unconsolidated entities relating to the Company's recognition of promoted interest		21,340	930
MVPI LLC | Joint Venture Agreement Modification [Member]
Summary of the Company's equity in income of unconsolidated entities
Payments for (Proceeds from) Other Real Estate Partnerships		20,680
Brandywine [Member]
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	10	(1,474)	828
CVP I, LLC
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	9	1,812	113,127
Equity in income of unconsolidated entities relating to the Company's recognition of promoted interest		1,289	61,218
Gain on sale of communities		50,478
Residual JV
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	(1,374)	11,582	3,547
Avalon Clarendon [Member]
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	(2,359)	0	0
Arna Valley View LP
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	0	0	2,406
Juanita Village
Summary of the Company's equity in income of unconsolidated entities
Equity in income of unconsolidated real estate entities	$ 0	$ 0	$ 3